ORCID

https://orcid.org/0009-0007-9638-0034

Date of Award

2026

Document Type

Dissertation

Degree Name

Philosophy (Ph.D)

Department

Psychology

First Advisor

Robin Wellington

Second Advisor

Wilson McDermut

Third Advisor

Melissa Peckins

Abstract

Schizophrenia and Schizotypal Personality Disorder (SPD) can be conceptualized along a schizophrenia spectrum characterized by overlapping clinical and neuroanatomical features, but differing levels of symptom severity and functional impairment. Although structural abnormalities in the frontal and temporal regions are well documented in schizophrenia, there are few studies that have examined individuals with true SPD, compared to both individuals with schizophrenia and healthy controls in one study using cortical surface area and thickness (as opposed to volume alone). The present study investigated neuroanatomical differences across the schizophrenia spectrum by examining cortical area, thickness, volume, and hemispheric asymmetry in the caudal middle frontal, rostral middle frontal, inferior temporal, middle temporal, and superior temporal regions. Participants consisted of healthy controls, individuals with SPD, and individuals with schizophrenia. Results found significant group differences in both frontal regions. Individuals with schizophrenia were found to be significantly reduced across area and thickness, and in volume in the rostral middle frontal compared to both SPD and healthy controls. In the caudal middle frontal region, the SPD group was found to be significantly greater across area and thickness in the caudal middle frontal region relative to both schizophrenia and healthy controls. In the inferior temporal region, healthy controls across area and thickness were greater than both SPD and schizophrenia. Exploratory analyses revealed group differences in middle temporal region in cortical thickness asymmetry. These findings support a dimensional spectrum model and suggest that increased frontal cortical surface area and thickness in SPD may reflect compensatory neuroanatomical mechanisms that reduce vulnerability to full psychosis. By distinguishing cortical surface area and thickness from overall volume, this study provides a clearer understanding of structural brain differences across the schizophrenia spectrum.

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